Thucydides: war and the polis -- Plato: who should rule? -- Aristotle: the best constitution -- Cicero: the idea of the republic -- St. Augustine: the city of God -- St. Thomas: faith and social solidarity -- Machiavelli: how to rule? -- Grotius: international society -- Hobbes: the beginning of modernity -- Locke: liberty and property -- Epilogue: the classics and the moderns -- The great debate.